| 摘要 |
PROBLEM TO BE SOLVED: To obtain a self-excited flyback converter in which an oscillation frequency is lowered at a light load and on standby and in which a power consumption by a main switching element is reduced, by a method wherein a circuit which is composed of a Zener diode used to clamp a flyback voltage and which is composed of a switching element constituting a bypass circuit is installed at the gate drive circuit of the main switching element. SOLUTION: A driving coil 13 is connected via a series circuit composed of a capacitor 4 and a resistance 6 in series across the gate and the source of a main switching element 1. In addition, a gate drive circuit is constituted in such a way that series circuit which is composed of a resistance 5 and a diode 7 as well as a Zener diode 8 provided with a switching element 9 at a bypass circuit is connected in parallel across the connection point of the capacitor 4 to the resistance 6 and one end of a driving coil 13. At this time, the switching element 9 is turned off at a light load, a voltage across both ends of a resistance 3 across the gate and the source of the main switching element 1 is lowered by a portion of the voltage of the Zener diode 8, the time in which the main switching element 1 is turned on becomes long, and an oscillation frequency is lowered.
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